Nothing could change our world, or about the world of [the believer’s] experience, that would demonstrate the falsity of many of their core beliefs. This proves that these beliefs are not born of any examination of the world, or of the world of their experience. (They are, in Karl Popper’s sense, “unfalsifiable.”)
It appears that even the Holocaust did not lead most Jews to doubt the existence of an omnipotent and benevolent God. If having half of your people systematically delivered to the furnace does not count as evidence against the notion that an all-powerful God is looking out for your interests, it seems reasonable to assume that nothing could.
(Sam Harris, The End of Faith, pp. 66-67)